Subnet Calc

subnetcalc

You can use the subnetcalc:// URL scheme to open Subnet Calc and Subnet Calc Pro starting the app at a certain subnet.

Application homepage: http://iphone.galloway.me.uk/subnetcalc
iTunes link: http://itunes.apple.com/gb/app/subnet-calc/id295652242
HTML Link example:
Native application URL string example: subnetcalc://192.168.0.1/24
Extended example: subnetcalc://192.168.0.1/24 subnetcalc://view?ip=192.168.0.1&cidr=24
Tags: ip,network,administrator,admin,administration

Self explanatory and simple URL scheme to open the app with the IP address and CIDR fields pre-filled in.